LITTLE ROCK (CFP) — More than 15 months before a single vote is cast for the U.S. Senate — indeed, before Arkansans even know for sure who will be running — outside groups from both sides of the political aisle have already dumped more than $1 million in ads onto TV viewers across the Natural State.

This spending wave is even more striking considering that Arkansas is the second-smallest Southern state, with fewer than 3 million people, and has only two major television markets.

Senator Mark Pryor

Incumbent Senator Mark Pryor, considered one of the most vulnerable Democrats in the 2014 election cycle, raised $1.2 million in the second quarter of 2013, with nearly $4 million in the bank, according to figures filed with the Federal Election Commission.

However, Pryor has already had to go up on TV to counter a negative ad from New York Mayor Mike Bloomberg’s group Mayors Against Illegal Guns, which poured $350,000 into Arkansas earlier this year.

Bloomberg’s spots lambasted Pryor for his vote against President Obama’s call for expanded background checks for gun purchases. In his reponse, Pryor said he was defending the Second Amendment against a proposal that wouldn’t have prevented any of the recent mass shootings.

All told, Pryor spent $700,000 in the second quarter, or nearly 60 percent of what he managed to raise during that period.

Representative Tom Cotton

Meanwhile, the man considered to Pryor’s likely GOP opponent, Representative Tom Cotton of Dardanelle, raised $611,000 during the second quarter and now has slightly more than $1 million in the bank.

Cotton, an Iraq war veteran in just his first term in the House, has been playing coy about whether he’ll give up his safe 4th District seat to challenge Pryor. He says he won’t make an annoucement on his plans until after the August congressional recess.

But national Democratic groups clearly think Cotton will run. In a pre-emptive strike, two outside liberal groups, Patriot Majority USA and the Senate Majority PAC, pummeled Cotton with $308,000 worth of TV attacks earlier this summer.

So far, Cotton has not felt the need to rebut those spots with ads of his own.

Another member of the state’s congressional delegation, Representative Steve Womack of Rogers, has said he, too, might run against Pryor. In the second quarter, Womack raised $123,000 with $600,000 on hand, putting him well behind Cotton.

A GOP primary is considered unlikely. Womack, who has been in the House since 2011, is not expected to make the Senate race if Cotton runs.

Pryor, scion of one of Arkansas’ most prominent political families, barely faced opposition when he ran for a second term in 2008. But Republicans are smelling blood in the water this time around, largely because of the senator’s vote in favor of Obamacare in 2009.

Obama is deeply unpopular in Arkansas, losing the state by 23 points in 2012.

Two outside conservative groups, the Club for Growth and Senate Conservatives Action, have already spent more than $500,000 in negative ads against Pryor.

The Club for Growth was one of Cotton’s major financial backers in his successful House race in 2012.